1. Field of the Invention
The invention relates to a facsimile transmission apparatus for transmitting the facsimile signal with high efficiency which is connected to a DSI (Digital Speech Interpolation) unit and a DCME (Digital Circuit Multiplication Equipment) unit in the line which includes voice signal and facsimile signal, for example, a public telephone circuit.
2. Description of the Prior Art
There are two kinds of prior art described hereinafter.
FIG. 9 is a block diagram of a conventional facsimile apparatus for demodulating and digitizing a facsimile signal and then transmitting it, and also for transmitting a facsimile signal without storing the facsimile signal, that is, operating in a real time operation.
In FIG. 9, 51 is a trunk side analog input port, 52 is a trunk side analog output port, 53 is facsimile modem (FAX modem), 54 is a multiplexer, 55 is a bearer side digital output port, 56 is a bearer side input port. The facsimile signal from the trunk side analog input port 51 is inputted to the FAX modem 53, demodulated in the FAX modem 53 and converted to a digital signal having a maximum bit rates of 9.6 kbit/s. The digital signal is transmitted to the multiplexer 54 and multiplexed to a higher speed multiplexed signal and is transmitted from the bearer side signal output port 55 to a remote side multiplexer 54 through a remote bearer side input port.
In the receiving side, the multiplexer 54 derives the digital facsimile signal having a maximum bit rate of 9.6 kbit/s from the high speed multiplexed signal received from the remote side multiplexer, and sends it to the FAX modem 53. The signal is modulated in the FAX modem 53 and converted into an analog signal, then transmitted to the trunk side output port 52.
In the conventional apparatus, an input facsimile signal goes through the apparatus without being stored in the apparatus, and is transmitted to the remote apparatus. Namely, the conventional apparatus operates as a real time operation apparatus. In the conventional apparatus, the input signal is restricted to the facsimile signal. Therefore, the voice signal which can not be transmitted to the FAX modem must be controlled to avoid being passed through the apparatus at the pre-stage of the trunk side port 51, 52. Also, the apparatus must be compatible with procedures which include all types of facsimile apparatus and its combinations. Therefore, procedures which are not compatible with the apparatus can not be used.
A number of FAX modems are able to operated in parallel within the range of the transmission capacity. Though each input is one analog line in the above description, it can use a digital input by providing a digital/analog converter in front of the trunk side input.
FIG. 10 shows another conventional art system in which the trunk side interface is the same as is in FIG. 9. In FIG. 10, 57 is a receiving facsimile modem (FAX modem), 58 is a transmitting FAX modem, 59 is a receiving data storage device, 60 is a transmitting data storage device. The input signal is inputted to the receiving FAX modem 57 from the trunk side port 51. The receiving FAX modem 57 terminates the facsimile signal in contrast with the FAX modem 53 of FIG. 9. The receiving FAX modem 57 operates in accordance with the same procedure for the remote side facsimile apparatus. The receiving FAX modem 57 sends the digital signal of the picture facsimile to the receiving data storage device 59. The receiving data storage device 59 stores the picture signal. In FIG. 9, the output of the FAX modem 53 includes the facsimile control signal, but the output of the apparatus in FIG. 10 includes only picture signal. The stored picture signal is transmitted to the bearer output port 55 under the control of the multiplexer 54 when there is available capacity on the bearer transmission line. The output signal is inputted to the remote side multiplexer 54 through the remote side input bearer port 56. The remote side multiplexer 54 derives the picture input signal from the high speed signal and stores it into the transmitting data storage device 60. The transmitting FAX modem 58 operates as a typical facsimile apparatus. The transmitting FAX modem 58 calls the designated destination facsimile and sends the picture data by the typical facsimile procedure when the call is connected. In the facsimile apparatus, the picture data are usually output to paper, but in this apparatus the picture data are stored in the transmitting data storage device 60. If the designated destination facsimile is busy, then the same operation is repeated.
In FIG. 10, the apparatus includes a plurality of the transmitting FAX modems 58, but if the capacity of the transmitting data storage device 60 is large, one transmitting FAX modems 58 will have the same function. If the number of the transmitting FAX modem 58 is small, the storage time becomes long and the advantage of the facsimile, that is in real time operation, is lost.
As explained above in FIG. 9, the conventional apparatus needs a facsimile signal for its input signal. That is, the apparatus provided at the trunk side shown in FIG. 9 must send only a facsimile signal to this facsimile transmission apparatus. In the case where the connected apparatus is discriminated in advance as a facsimile apparatus or a telephone set, for example, such as in a PBX system, this facsimile transmission apparatus can be used if the facsimile signal is selectively transmitted to the facsimile transmission apparatus. This facsimile transmission apparatus must correspond to all facsimile signals. There are many facsimile procedures, for example, tonal procedure, and binary procedure. CCITT recommendation T. 30 allows use of other non-standard procedures which are used only in some manufactures. In the conventional apparatus shown in FIG. 9, the facsimile transmission apparatus can be used only for the system which corresponds to the particular facsimile apparatus. Therefore, if the facsimile transmission apparatus procedure is not compatible with the facsimile apparatus procedure, the facsimile transmission apparatus can not be used with a public telephone circuit which includes many non-compatible procedures.
The apparatus provided at the trunk side shown in FIG. 10 must send only a facsimile signal to this facsimile transmission apparatus in the same way as is in FIG. 9.
The facsimile transmission procedure need not be compatible with all procedures described in FIG. 9. It may receive the signal by a procedure which corresponds to the facsimile transmission procedure. The facsimile transmission apparatus is able to transmit the signal by its own procedures at the output transmitting side. In FIG. 10, since the facsimile transmission apparatus terminates and stores the signal, time delay becomes large. Therefore, the apparatus practically can not be used with a the public telephone circuit which operates on a time basis.
Accordingly, it is an object of the present invention to provide a facsimile transmission apparatus which can be used for all types of public telephone circuits and which is not restricted by a particular kind of facsimile apparatus.
It is further object of the present invention to provide a facsimile transmission apparatus which increases the bearer side efficiency compared with the facsimile transmission apparatus using only DCME and DSI.
It is still further object of the present invention to provide a facsimile transmission apparatus which permits a decrease in the number of the FAX modems.